The historically important ruins of a small brick and sandstone temple in very poor condition. The earliest elements date from the pre-Angkorian 8thcentury, Inscriptions indicate that a temple dedicated to the Hindu ‘god of the depths’ was previously located on the same spot. Ak Yum is the earliest known example of the ‘temple-mountain’ architectural design formula, which was to become a primary design formula for many of the Angkorian period temples including Angkor Wat.